Purpose: We established diagnostic accuracy in terms of the sensitivity and specificity with which a rigorously trained canine olfactory system could recognize specific volatile organic compounds of prostate cancer in urine samples.Materials And Methods: Two 3-year-old female German Shepherd Explosion Detection Dogs were trained to identify prostate cancer specific volatile organic compounds in urine samples. They were tested on 362 patients with prostate cancer (range low risk to metastatic) and on 540 healthy controls with no nonneoplastic disease or nonprostatic tumor.